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Sowbugs and Pillbugs

- Tiny armadillos! -

Summary: Normally these small crustaceans don't harm anything in the garden. Occasionally, however, the populations may grow and begin to feed on and damage seedlings. At these times steps should be taken to protect young plants.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

Sowbugs, pillbugs or woodlice [more pictures] normally don't harm garden plants. They feed mostly on dead organic debris. However, two situations occur that cause gardeners and homeowners some concern.

Sometimes these small land crustaceans (related to shrimp) damage tender, young garden seedlings -- their damage is similar to slug damage. This plant damage only occurs when very high populations of these critters are allowed to develop and when very young plants are present. Plant injury is pretty rare and can usually be managed.

other common names: woodlice (wood louse), lawn shrimp, rollie-pollie (pillbug), rolly-polly, tumblebug, doodlebug

sowbugs and pillbugs

Sowbugs and pillbugs are found in moist habitats under rocks and debris. Photo by E. DeAngelis copyright 2006

 

The second way sowbugs and pillbugs get noticed is by sheer numbers. They can sometimes occur in such high numbers that they alarm people. They may enter houses following rains when outside soils become saturated. Sowbugs found indoors won't cause any damage and can be simply swept up. Pillbugs roll into a ball when distrubed, sowbugs do not roll up this way.

Can sowbugs and pillbugs be managed?

In one sense high numbers of these critters is a good thing -- it means that your garden soils are rich in organic matter and healthy. You can reduce the populations, however, by reducing the amount of organic matter that you add to the garden and cutting back on the frequency of watering. If the soil is allowed to go through natural dry/wet cycle sowbug and pillbug numbers will be reduced.

Protect seedlings with diatomaceous earth

Gardeners can use diatomaceous earth to manage sowbug and pillbug damage to young seedlings. Place a thin layer of this natural product directly over the seed bed. There is also a new formulation of Sluggo slug bait that contains spinosad, a natural insecticide that can be used to safely manage earwigs and sowbugs/pillbugs in the garden (right).

Finally, there are synthetic insecticides, for example carbaryl, that can be used for sowbug/pillbug control. Check your local garden store's insecticide shelf and look for sowbugs or pillbugs on the product labels.

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Identification guides, reference and gardening books, etc.

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Jack DeAngelis, Ph.D.

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